Silicon-substituted hydroxyapatite coating with Si content on the nanotube-formed Ti-Nb-Zr alloy using electron beam-physical vapor deposition

The purpose of this study was to investigate the electrochemical characteristics of silicon-substituted hydroxyapatite coatings on the nanotube-formed Ti-35Nb-10Zr alloy. The silicon-substituted hydroxyapatite (Si-HA) coatings on the nanotube structure were deposited by electron beam-physical vapor deposition and anodization methods, and biodegradation properties were analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy measurement. The surface characteristics were analyzed by field-emission scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD). The Si-HA layers were deposited with rough features having highly ordered nanotube structures on the titanium alloy substrate. The thickness of the Si-HA coating was less than that of the HA coating. The XRD results confirmed that the Si-HA coating on the nanotube structure consisted of TiO2 anatase, TiO2 rutile, hydroxyapatite, and calcium phosphate silicate. The Si-HA coating surface exhibited lower Icorr than the HA coating, and the polarization resistance was increased by substitution of silicon in hydroxyapatite.